SYNTHESIS OF THE ACYLTETRONIC ACID IONOPHORE TETRONASIN (ICI-M139603)

A synthetic strategy for the preparation of tetronasin 1, an acyltetro nic acid ionophore demonstrating antibiotic, antiparasitic and growth promotion in ruminants is described. The key step involves a metal med iated cyclization reaction which creates two rings and four new stereo centres in a highly efficient manner. The configurations of three of t hese stereocentres are as required for the synthesis of tetronasin. Th e remaining stereocentre is readily epimerised to the natural configur ation at a later stage of the synthesis.